Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H, W = map(int,input().split())
G = [input() for _ in range(H)]
white = 0
dist = [(-1, 0), (1, 0), (0, -1), (0, 1)]
visited = set()
for line in G:
  white+=line.count('.')

D = deque()
D.append((0,0,1))
rout = -1
while D:
  h, w, c = D.popleft()
  if h == H-1 and w == W-1:
    rout = c
    break
  if (h, w) in visited or G[h][w] == '#':
    continue
  else:
    visited.add((h, w))
  for dh, dw in dist:
    if (0<=h+dh<H) and (0<=w+dw<W):
      if (h+dh, w+dw) not in visited and G[h+dh][w+dw] != '#':
        D.append((h+dh, w+dw, c+1))
        
if rout == -1:
  print(rout)
else:
  print(white-rout)